The best thing you can do , is to get vent visors for the window. Then leave the windows cracked open to the bottom of the vent visor. That inch and a quarter or so, per window, will lower the interior temps drastically - vs a truck with closed windows. Of course, the vent visors will keep the rain out if it happens.
The paint, who knows, this is my first dodge truck. My tahoe sat in the sun every day for six years and was fine. Keep it washed and conditioned (sealer or wax) regularly, and it will be fine.